This invention relates to security paper, i.e. paper which is resistant to counterfeiting or other attempts at fraudulent imitation and which is suitable for use in the production of security documents.
By a "security paper" or "security document" is meant any paper or document having a value such as to render it potentially liable to attempts at counterfeiting. Typical examples of such papers or documents are papers for use in passports; banknotes; cheques; travellers cheques; money orders; bankers drafts; bearer bonds; share certificates and other certificates; stamps; postal orders; identity documents; registration documents, driving licences, vehicle road tax licences and other licences or permits; electoral papers; savings or bank account passbooks; lottery tickets; admission tickets; travel tickets; vouchers; coupons; tokens; and shipping and other transport documents.
Papers for use in labels or distinctive packaging may also be subject to counterfeiting, particularly if they bear a manufacturer's name and/or a brand name. Considerable publicity has been given in recent years to the problems of illegal marketing of cheap copies of branded goods, for example car brake pads, and prestigious brands of wristwatch or clothing, and of illegal copying of pre-recorded music cassettes, records or videotapes or of computer programs. The copies are liable to be packaged and branded in much the same way as genuine goods from an original or authorised manufacturer. Thus the use of verifiable paper in the labels and/or packaging of the goods provides a means of checking the authenticity of branded goods. Verifiable label or packaging paper is therefore also within the ambit of the term "security paper" as used in this specification.
High security documents, such as passports and banknotes, often carry a tactilely-detectable surface profile pattern or design (hereafter referred to simply as a "tactile pattern") which is imparted to selected areas of the finished paper at the printing stage. The tactile effect can be produced by embossing, or by the use of special inks which stand proud of the paper even after drying, or a combination of embossing and special inks. The tactile pattern enables the document to be partially authenticated by touch, in that a document with no such selective tactile pattern is immediately revealed as counterfeit. An example of the use of a selective tactile security pattern is the internal end paper for UK-issued passports. The tactile pattern enables inspecting officers quickly to verify the document by touch.
Conventional dry embossed patterns suffer from the drawbacks that they increase production costs at the printing stage, and that they can wear away in use. The intricacy of the pattern applied, and thus the level of security obtainable, is also limited when the pattern is produced by embossing previously formed and dried paper.
It is an object of the invention to overcome the drawbacks just described.
It is known to produce a surface texture on a still wet web of paper on the papermachine before the web has been dried. Such textures may be applied by means of the press felts ("felt marking") or by embossing rolls or belts, see for example British Patent Application No. 2270931A. However such textures have been applied over the entire surface of the paper and are relatively simple and lacking in depth and/or fine detail. It is also known to "rubber mark" papers in the press section of the papermachine by means of rubber stereos mounted on one or both of a pair of cooperating press rolls. Such marking is usually used to apply a brand name, manufacturer's name or a logo, i.e. relatively simple designs.